BMW uses many different connector types. In this post I'm going to go over the two types I've come to understand pretty well.
Choose the connector family before ordering
- Round 2.5 mm pin/socket contacts: compare the original terminal, then choose the round-contact depin tool and matching replacement pins or sockets. The round-pin identification guide explains the checks.
- Bosch-style connector housings shown below: use the Bosch-style depinning tool for a compatible serviceable housing. For replacement housings, see the 2-, 3-, 4- and 5-pin Bosch guide.
Connector names such as C101 or X20 are a starting point, not a complete fitment check. Compare the mating face, terminal shape, locking system and wire size. Unsure? Send clear connector photos before ordering.
The first type uses 2.5mm circular male and female terminals. Some connectors that use these types of pins include but are not limited to the following: C101, C191, X20, X69, X6031, X33
In the image below you can see the male and female pins circled in red.
I also developed a de-pinning tool to help with any custom wiring or restoration jobs.
These depin tools can be found here. I also have the 2.5mm pins available for purchase.
Some of these connectors can be a little tricky. In the image below see how the connector can become locked. This is the c101 connector. It is a two part assembly. There are two plastic concentric parts that rotate and index into different positions. Depinning should not require much force. Study your connector and make sure it doesn't have a locking mechanism.
Now moving on to the next connectors that are commonly used on these cars. These are the Bosch style connectors. Below are a 5-pin female and 2-pin male style.
Some original Bosch-style housings have heat-staked retainers like the examples shown below. Inspect your housing before attempting to remove the terminals.
Circled in red you can see where they heated up the connector and pressed down into the cavity where the wires are. This prevents the wire from being evacuated. Even if you have the correct de-pinning tool, the wire will get stuck and not back-out all they way.
Here you can see where that little nub is.
For a heat-staked or damaged housing, a matching replacement may be the practical repair. Compare the mating face, keying, latch, terminals and seals before ordering. The Bosch-style tool linked below is for compatible serviceable housings; it does not remove a heat-staked obstruction.
Need a custom BMW wiring harness?
Falk Manufacturing builds custom and small-run BMW adapter harnesses. The M20-to-M50 TPS adapter harness shown here is one example of a clean, reversible connector conversion that avoids cutting the original engine harness.
Have a different connector conversion or harness-repair project? Email info@falkmfg.com with the vehicle year and model, engine and ECU information, clear photos of both connector faces, and any available pinout information. I’ll review the project and do my best to develop a solution for you.
View the M20-to-M50 TPS harness example →